Methods of making a tubular member having a sealed longitudinal seam

ABSTRACT

SUCCESSIVE PORTIONS OF AN ALUMINUM TAPE HAVING ONE MAJOR SURFACE THEREOF COATED WITH AN ADHESIVE COPOLYMER ACROSS THE ENTIRE TRANSVERSE WIDTH THEREOF AND THE OTHER MAJOR SURFACE PRECOATED WITH A STRIPE OF ADHESIVE MATERIAL ALONG AN EDGE PORTION ARE FOLDED LONGITUDINALLY AS THE SUCCESSIVE SECTIONS OF THE TAPE ARE BEING ADVANCED ALONG A PREDETERMINED PATH TO FORM AN OVERLAPPED SEAM SO THAT THE ADHESIVE COPOLYMER ON AN EDGE PORTION OF THE ONE MAJOR SURFACE OF THE TAPE OVERLAPS THE STRIPE. SUBSEQUENTLY, THE ADHESIVE MATERIALS ON THE MAJOR SURFACES ALONG THE OVERLAPPED SEAM DEVELOP AN ADHESIVE BOND BY THE APPLICATION OF HEAT AND PRESSURE PRIOR TO OR DURING THE EXTRUSION OF A PLASTIC JACKET OVER THE TAPE. THE ADHESIVE MATERIAL ON THE OTHER, NOW INWARDLY FACING, MAJOR SURFACE IS SUBSTANTIALLY RESTRICTED IN LOCATION AND IS ADHESIVELY BONDED TO THE PORTION OF THE INWARDLY FACING MAJOR SURFACE OF THE TAPE WHICH FORMS THE OVERLAPPED SEAM WITH A PORTION OF THE ONE, NOW OUTWARDLY FACING, MAJOR SURFACE. THE REMAINING PORTION OF THE INWARDLY FACING MAJOR SURFACE OF THE ALUMINUM TAPE IS BARE AND THE RESULTING TUBULAR MEMBER MAY BE USED IN A VARIETY OF WAYS.

Aug. 13, 1914 M. R. DEMBIAK ETAL 3,829,340 METHOD OF MAKING A TUBULARMBER HAVING SEALED L ITUDIN SEAN 'ginal Fil March 24, 1969 2| F/GZ I rI7 5" W x i Y QS Q l 16 14 9 I I9 22 1 v United States Patent O3,829,340 METHODS OF MAKING A TUBULAR MEMBER HAVING A SEALEDLONGITUDINAL SEAM Matthew R. Dembiak, Clifton, NJ., and George H.Webster, Timonium, Md.; said Dembiak assignor to Western ElectricCompany, Incorporated, New York, N.Y., and said Webster assignor to BellTelephone Laboratories, Incorporated, Murray Hill, NJ. Application Mar.17, 1971, Ser. No. 125,362, now Patent No. 3,703,605, which is acontinuation of abandoned application Ser. No. 809,589, Mar. 24, 1969.Divided and this application Aug. 2, 1972, Ser. No. 277,188 Int. Cl.B29d 23/10 US. Cl. 156-201 Claims ABSTRACT OF THE DISCLOSURE Successiveportions of an aluminum tape having one major surface thereof coatedwith an adhesive copolymer across the entire transverse width thereofand the other major surface precoated with a stripe of adhesive materialalong an edge portion are folded longitudinally as the successivesections of the tape are being advanced along a predetermined path toform an overlapped seam so that the adhesive copolymer on an edgeportion of the one major surface of the tape overlaps the stripe.Subsequently, the adhesive materials on the major surfaces along theoverlapped seam develop an adhesive bond by the application of heat andpressure prior to or during the extrusion of a plastic jacket over thetape. The adhesive material on the other, now inwardly facing, majorsurface is substantially restricted in location and is adhesively bondedto the portion of the inwardly facing major surface of the tape whichforms the overlapped seam with a portion of the one, now outwardlyfacing, major surface. The remaining portion of the inwardly facingmajor surface of the aluminum tape is bare and the resulting tubularmember may be used in a variety of ways.

CROSS REFERENCE TO RELATED APPLICATIONS This appliction is a division ofSer. No. 125,362, now US. Pat. 3,703,605, which is a continuingapplication of applicants copending application Ser. No. 809,589 filedMar. 24, 1969 now abandoned.

BACKGROUND OF THE INVENTION 1. Field of the Invention This inventionrelates to methods of making a tubular member having a sealedlongitudinal seam, and more particularly, to methods of making a tubularmember in which successive portions of a metallic tape are precoated onat least part of one major surface with an adhesive copolymer materialand along an edge portion on the other major surface with a stripe ofadhesive material and then wrapped longitudinally to form an overlappedseam with an adhesive bond occurring between the adhesive materials onthe overlapped portions of the tape.

2. Technical Considerations and the Prior Art It is known that changesin the ambient conditions lead to difierences in vapor pressure betweenthe inside and the outside of a plastic covered tubular member whichgenerally operates to diffuse moisture in a unidirectional manner fromthe outside of the tubular member to the inside thereof. This eventuallywill lead to an undesirably high moisture level inside the tubularmember, especially if a polyethylene jacket is the only barrier to theingress of the moisture high.

A metallic laminate which is wrapped longitudinally to form a tubularmember is an effective barrier against diffusion of moisture into thecore.

3,829,340 Patented Aug. 13, 1974 The laminate may be made from a singlestrip of metal, such as aluminum, in the form of a tape, which iswrapped longitudinally about the cable to overlap the edge portions.After the metallic tape of, say aluminum, is folded about the core toform a tube, an outer jacket of polyethylene may be extruded over thetube depending on the requirements of the final product. As thepolyethylene cools, the polyethylene material contracts. The coolingproceeds from the outer surface of the jacket inwardly with theshrinkage forcing the polyethylene into close engagement with thesurface of the longitudinally folded tape and slides the overlappingedge portions of the metallic tape relative to each other to partiallycollapse the shield. The relative sliding movement of the overlappingedge portions is stopped when the tubular shield is supported againstthe core. During this shrinkage, the outer overlapping edge of thefolded tape presses outwardly into the plastic jacket, thereuponreducing the effective jacket thickness radially outward from the tapeedge.

The slippage along the seam may be eliminated and the effectiveness ofthe strip as a moisture barrier or shield enhanced substantially if theseam between the overlapping edges is sealed. More particularly, a sealis most effective in which a metal-to-metal bond of the overlapping edgeportions is accomplished, for example, by welding or soldering.Generally though, the materials which may be the core aretemperature-sensitive and easily damaged if overheated. Thesecharacteristics render the use of welding, as a sealing technique,impractical because of the high temperature involved in most ordinarywelding processes. Moreover, the aluminum, because of its highlyreactive nature, generally maintains an oxide film which vitallyprecludes continuous soldering as a joining technique. Therefore, othermethods have been devised for sealing the overlapping edges of the seamof the aluminum, longitudinally wrapped, laminate.

In order to improve the corrosion resistance of the laminate andeliminate the slippage along the overlapping seam, a special adhesivecopolymer consisting essentially of a polyethylene in form with attachedcarboxyl groups may be applied both sides of the metallic tape. Theadhesive copolymer which is an ethylene acid copolymer or morepartticularly, an ethylene acrylic acid copolymer, is applied in theform of a flexible protective film and has high electrical resistivity,high resistance to chemicals and moisture, and especially good adhesionto the aluminum to withstand both manufacturing processes, such ascorrupgating and longitudinal folding, and to prevent delaminations incorrosive environments. The application of adhesive copolymers inlaminates is discussed by B. Wargotz in an article EnvironmentalStability of Ethylene-Acrylic Acid Adhesive Copolymers Bonded to MetalSubstrates published in Vol. 12 of the Journal of Applied PolymerScience, pages 1873-1888 (1968). Adhesive copolymers such as thesedevelop a firm bond between the metallic strip and the outerpolyethylene jacket.

Adhesively sealed metallic moisture barriers may be manufactured withoutresort to an overlapped seam. Metal tapes, for example, have been formedinto finned configurations wherein the two edge portions of alongitudinally applied tape are oriented radially of a cable core withthe polymer coatings on the inner surfaces of each of these edgeportions being in contact. The two edge portions are then heated andpressed to form a bond between the two copolymer coatings. Theprojecting sealed fin is then folded down to lie substantially parallelto the main portion of the formed tape. The sealing of the fin issometimes accomplished by the heat of a polymeric jacket extruded overthe metal tape rather than in a separate sealing operation.

The use of this finned seam system results in at least three thicknessesof materials along some part of the periphery of the metal tape andthese multiple thicknesses of material add to the non-uniformity in thethickness of a polymeric jacket applied over the metal tape. The formingand sealing of the fin type seam is much more difiicult than forming anoverlap seam.

A metallic, for example, aluminum tape, may be precoated on both majorsurfaces with the adhesive copolymer, across the entire width thereof,after which the precoated tape is folded longitudinally about the core.When a polyethylene jacket is applied over the core and metallicshielding layer, the heat from the semimolten polyethylene extrudedaround the shielding layer bonds the metal strip to the polyethylenejacket. If the heat imparted to the polyethylene material issufficiently high, the aluminum tape Will become hot enough so thatbonding will also occur between overlapped layers of the shielding layerat the seam. The coated metallic tape firmly adheres to the outer jacketto further inhibit the penetration of moisture. The use of a shieldinglayer with a sealed seam also has been shown to have higher strengthcharacteristics necessary to withstand repetitious bending of the cable.

Although the desired bond between the outer jacket and the core and theprevention of moisture penetration is solved by the use of a fullybonded sheath such as that described above, problems arise in some uses.For example, it may be required that the polyethylene jacket be removedfrom the aluminum tape or that a clamp be placed in contact with theinner surface of the metallic tape. An ear is formed at each end of thesheath clamp which protrudes through slots cut in the metallic tape andare exposed for engagement with a grounding clamp. Because of theintimate bond between the metallic tape and the jacket and between themetallic tape and the copolymer coating, it is difficult to bare themetallic tape to develop, say, electrical contact at the splice locationto assure that the shielding function of the aluminum tape takes place.

Of course, the tubular member could be manufactured with something lessthan an intimate bond between the jacket and the laminate to facilitatesplicing and grounding while still providing corrosion protection forthe metal tape. In at least one prior art patent, firm adhesion of theadhesive copolymer is restricted to only a portion of the interfacebetween the jacket and the laminate. More specifically, the metallictape is coated with a reactive carboxyl group material only along thelongitudinal edge portions and for a limited predetermined distance oneach side of the tape from the edges. The remainder of the tape iscoated with a material having less adhesive qualities or may be coatedwith the same material over the entire width and then treated along aportion thereof intermediate the edges to reduce the adhesivecharacteristics of the coating in the portion intermediate the edges.(See US. Pat. 3,379,821 issued Apr. 23, 1968.)

However, any reduction in adhesive at the interface will be matched by acorresponding reduction in the absolute resistance to moisturepenetration. In the construction just described, protection againstmoisture penetration depends upon a sealed seam. The absence of anintimate bond between the jacket and the laminate around the majority ofthe periphery of the tubular member presents the possibility of moisturepenetration through pin holes with subsequent travel of the moisturealong the length of the tubular member between the jacket and thelaminate.

In many types of cable seam constructions, the sealing of the overlapdepends upon the development of an adhesive bond between an adhesive,say precoated on one of the overlapping metallic portions to the otheruncoated metallic portion, or say the development of an adhesive bond ofan adhesive tape to both metallic overlapping portions of the metallicshield.

It is therefore an object of this invention to provide methods ofmanufacturing tubular members having a metallic laminate with anoverlapped seam sealed with the requisite integrity by developing anadhesive'bond'between two adjacent contiguous adhesive materials at theoverlapped seam and having portions of the laminate bare for splicingpurposes.

Of course, it is possible to merely coat one major surface of thealuminum strip with the adhesive copolymer. However, there would then beno adhesive on the other major surface to bond with the adhesive on theone major surface along the overlapped edge portions at the seam to formthe desired sealed seam. In order to obtain a reliably sealed scam, theother major surface of the aluminum strip is preferably coated at leastalong the edge portion thereof with an adhesive material.

However, methods have not priorly been developed in which only a portionof one major surface is coated with adhesive copolymer material. Thiswas due in part to the fact that if a plurality of strips of adhesivecopolymer material were extruded on a web of aluminum, for example, andthen wound on a take-up reel, the resulting roll, having an enlargeddiameter alternating with voids across the transverse width of the rollbecause of the buildup of strips, would be exceedingly difficult tohandle and slit.

Therefore, it is an object of this invention to provide a tubular memberin which one major surface of a metallic tape is precoated across theentire transverse width thereof with a first adhesive copolymer materialand the other major surface has a stripe of a second adhesive materialselectively applied on the tape to bond with the first adhesive materialon the one major surface.

The term facing as employed in this specification and claims appendedthereto when referring to the relationship between a surface and anobject Will be understood to mean that the surface is oriented in thedirection of the object and may be, but is not necessarily, adjacent toor in contact with the object.

The term major surface as employed in this specification and appendedclaims when referring to surfaces of a strip of material or tape shouldbe understood to include the large faces of the strip and not the edgesof the strip even though the faces might have curved, corrugated orotherwise nonplanar configurations and even though the edges might blendsmoothl into the faces without any sharp geometrical definition.

The term polymeric material as employed in this specification andappended claims will be understood to include both thermoplasticcompounds such as polyethylene and polyvinyl chloride or the like,thermosetting compounds such as epoxies and polyurethanes and elastomerssuch as neoprenes.

SUMMARY OF THE INVENTION A method of manufacturing a tubular member andillustrating certain features of the invention may include the steps ofadvancing successive sections of at least one longitudinal tape along apredetermined path, forming successive portions of the tape into atubular shape with at least one overlapped seam and such that the radiusof curvature of the tape is substantially equal to the radius ofcurvature of the tubular shape, the tape having adhesive materialprecoated on at least part of an edge portion of one of the majorsurfaces of the tape forming the overlapping seam, the tape also havingadhesive material precoated on at least part of the other major surfaceof the tape along an edge portion thereof With the adhesive material onthe other major surface being at least adhesively bonded to the portionof the other major surface of the tape which forms the overlapped seamwith a portion of the one major surface, the remaining portion of theother major surface of the tape being at least partially bare, theadhesive materials on the major surfaces capable of developing anadhesive bond along the overlapped seam at a predetermined temperatureto seal the seam, and applying heat to successive portions of theoverlapped seam to elevate the temperature to the temperature at whichthe adhesive bond occurs.

Additional advantages and features of the invention will be bettercomprehended by reference to the drawing and the detailed descriptionswhich follow.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a cross-sectional view of atubular member taken transverse to a longitudinal axis of the tubularmember with a laminate, which includes a metallic tape, wrappedlongitudinally with an overlapped seam, to bond an adhesive material onan outwardly facing major surface of the tape to a stripe of adhesivematerial on an inwardly facing major surface and in some applicationshaving a jacket extruded thereover;

FIG. 2 is a cross-sectional view of the metallic tape taken transverseto a longitudinal axis of the tape and showing an adhesive materialcoated over the full transverse width of one major surface of the tapeand a stripe of adhesive material on the other major surface adjacent alongitudinal edge thereof;

FIG. 3 is a view showing the tubular member at a splice location with aportion of the laminate and jacket cut away from the core to permitinsertion of a grounding ring at the splice location;

FIG. 4 is a sectional view of a tubular member taken transverse to thelongitudinal axis of the tubular member manufactured in accordance withthe principles of the method of this invention with a laminate having asealed longitudinal seam and having provisions for grounding anoutwardly facing major surface of the laminate; and

FIG. 5 is a simplified view of an apparatus for carrying out the stepsof the method which embodies the principles of this invention to foldsuccessive portions of the metallic tape, precoated across the fullwidth of one major surface with a first adhesive material and having astripe of a second adhesive material adjacent a longitudinal edge on theother major surface.

DETAILED DESCRIPTION Referring now to FIG. 1, there is shown a tubularmember designated generally by the numeral 10, and having a hollow core12. The core 12 is coextensive with the tubular member 10, The core 12may include one or a plurality of conductors 11-11 (see FIG. 4).

Accordingly, to protect the core 12, a laminate, designated generally bythe numeral 13 (see FIG. 2), is wrapped longitudinally (see FIG. I). Asis shown in FIG. 2, the laminate 13 includes a metallic tape 14. Thelaminate 13, prevents the diffusion of water vapor interior of thetubular member 10.

The metallic tape 14 surrounds the core 12 with inwardly and outwardlyfacing major surfaces 16 and 17, respectively (see FIG. 2), of the tapein overlapped relation with each other along longitudinal edge portionsthereof to form a seam 18 (see FIG. 1). The radius of curvature of themetallic tape 14 which surrounds the core 12 is substantially equal tothe radius of curvature of the core. In the one type of constructionshown in FIG. 1, which embodies the principles of this invention, themajor surface 16 of the tape 14 faces inwardly toward the core 12, whilethe major surface 17 faces outwardly in order to overcome the problemsdiscussed hereinbefore, the longitudinal seam 18 must preferably besealed while simultaneously making provisions for grounding the metallictape 14 at splicing locations.

The major surfaces 16 and 17 of the aluminum tape 14 are selectivelycoated with adhesive materials at least along the portions theerof whichform the overlapped seam prior to assembly with the core 12, so that theadhesive on the inwardly facing major surface 16 bonds with theoverlapped portions thereof while simultaneously prothe outwardly facingmajor surface 17 along the viding a structure which exposes the inwardlyfacing major surface 16 of the laminate 13 adjacent the core 12 (se FIG.1). By developing a bond of adhesive material with adhesive material, amore reliably sealed seam 18 is obtained than by using methods whichattempt to develop an adhesive-to-metal bond during the forming of theoverlapped seam.

A stripe 19 of an adhesive copolymer material is applied longitudinallyonto the inwardly facing major surface 16 of the aluminum tape 14 alonga peripheral edge portion thereof (see FIG. 2). Additionally, anadhesive copolymer material is applied on the outwardly facing majorsurface 17 of the metallic tape 14 across the entire transverse widththereof to form a film 21 (see FIG. 2). In this way, the peripheral edgeportion of the adhesive film 21 on the outwardly facing major surface 17is in engagement with and develops an adhesive bond with the stripe 19on the peripheral edge portion of the inwardly facing major surface 16of the tape 14 to seal the overlapping surfaces along the seam 18 (seeFIG. 1).

The film 21 on the outwardly facing major surface 17 is an adhesivematerial which has the ability to develop firm adhesion to the metallictape 14, and is highly resistant to corrosion and inhibits penetrationof moisture into the core. Moreover, the adhesive material develops afirm bond with an overlying polyethylene jacket 22 (see FIG. 1), whichis extruded over the laminate 13. The adhesive materials which comprisethe film 21 and the stripe 19 are selected so that when the laminate 13is wrapped around the core 12, the film and the stripe, under theapplication of heat, to raise the temperature to a predeterminedtemperature above ambient temperature, and pressure, are caused todevelop a bond to seal the seam 18.

The materials of the stripe 19 and the film 21 on the inwardly andoutwardly facing major surfaces 16 and 17- respectively, are comprisedof ethylene acid copolymers. Although the materials of the stripe 19 andthe film 21 may be adhesive copolymers having the same composition, thecomposition of the stripe is determined by the method used to form thestripe of a required thickness on the inwardly facing surface of thetape 14. For example, the film 21 is generally extruded over theoutwardly facing major surface 17; if the stripe 19 could beextrusioncoated onto the major surface 17, the composition of thematerial in the stripe could be of the same composition as that in thefilm.

However, diificulties are encountered in attempting to extrude with athin stripe of the desired dimension. In order to avoid the difiicultiesof slitting due to build-up on successive layers of a wound roll oflaminate 13, it may be desirous that the thickness of the stripe 19 issubstantially less than the thickness of the film 21 on the laminate 13.

Therefore, a copolymer solution may 'be used and the stripe 19 ispainted, rolled or printed by conventional coating techniques on themajor surface 17. Accordingly, the melt index and the acrylic acidcontent of the material of which the stripe 19 is comprised must besubstantially greater than the melt index and the acrylic acid contentof the material of which the film 21 is comprised. The acrylic acidcontent and the melt index of the copolymer must be adjusted, e.g.,15-20 percent acrylic acid content, -200 melt index, so as to easilydisperse the copolymer into solution.

Both the material for the stripe 19 and the material for the film 21 areavailable from commercial sources. For example, the film 21 may becomposed of methylene acrylic acid copolymer such as that marketed byDow Chemical Company of Midland, Mich. under the designation QX2375.0.Some examples of the copolymers for striping which are marketed arethose of Union Carbide Company, under the designation EAA resin 9500,and by E. I. du Pont de Nemours and Company under the trademark Surlyn Ddispersions.

Because of the properties of the QX2375 it is difficult to put thematerial into acqueous solution to get the required thickness of stripe.The QX2375 material has a.

melt index of approximately 5.0 and an acrylic acid content of 6-8percent by weight. If the acrylic acid content were much higher, theadhesive would not bond to the jacket; i'f lower, the adhesive bondsbetter to the jacket, but then there is difficulty in bonding to thealuminum tape. The 6-8 percent acrylic acid content i therefore acompromise.

To achieve the thin stripe 19 required, e.g., A to /2 mil, the copolymermaterial of the stripe must be tailored to easily disperse intosolution. The EAA 9500 has a melt index of 150-200 and an acrylic acidcontent of percent. The acrylic acid content is high to compensate forthe higher melt index and hence the weaker polymer. The acrylic acidcontent serves as a hardening agent, and acts as a gripping agent asbetween the aluminum tape 14 and the resin to give the requisite bondstrength. If the acrylic acid content were to be reduced, the bondstrength between the aluminum and the adhesive or between the adhesivematerials will be reduced accordingly.

The EAA resin 9500 and the Surlyn D materials are both generic to saltsof acrylic acid, the EAA 9500 being an ammonium salt, and the Surlyn Dbeing an alkaline metal salt. During the striping and curing process,the EAA 9500 is treated with ammonium to make an ammonia solution, theammonia driven off from the EAA 9500 striping solution before drivingoff the water with an ethylene acrylic acid stripe 12 resulting whichhasproperties different from those of the material of the film 21, e.g.,the melt index and the acrylic acid content. But by using the Surlyn Ddispersion, a salt is generated, as opposed to the acid of the EAA 9500,with the result that the stripe is composed of an acid and a complexsalt. The Surlyn D may be treated with sodium hydroxide or zinc salt tomake an alkali metal salt.

A solution of these copolymers may be effected by dispersing an acidcopolymer in either an organic solvent or in water.

Generally, the stripe 19 is applied from a solution which is obtained bydispersing a high melt index ethylene acrylic acid copolymer of greaterthan fifteen percent by weight acrylic acid in water which containsammonium hydroxide. A salt of ethylene acrylic acid is formed which iscoated onto the aluminum and dried.

Also, generally the material of the film 21 is selected so as to have alower melting point than the material of the stripe 19. In this way,heat transfer takes place through the stripe 19 so that the film 21contiguous with the stripe along the seam 18' melts and bonds to thestripe to seal the seam.

The physical size of the overlapping seam 18 is an important factor inthe ability of the laminate 13 to prevent diffusion of water into thetubular member 10. The rate at which water vapor diffuses through amaterial is proportional to the area which is exposed to the source ofwater vapor and the rate of diffusion is increasingly inverselyproportional to the length of the path through which the water vapormust travel. It should be apparent that as the overlapped seam 18 of thelaminate 13 is increased in width and as the thickness of the adhesiveseal in the seam decreases, the ability of the adhesive seal to preventmoisture diffusion is increased. As a practical matter, it becomesnecessary to assign definite dimensions to the seal. Cost andmanufactuirng considerations are factors which have led to adetermination of optimum dimensions for the adhesive seal.

By applying a stripe 19 of adhesive material along an edge portion ofthe aluminum tape 14 along the inwardly facing major surfaces 16thereof, and then coating the entire outwardly facing major surface 17with the adhesive copolymer film 21, the mating major surfaces 16 and17, along the overlapped edges, form the sealed seam 18- and a moistureresistant tubular shield is formed around the core 12. The resistance ofthe tubular member 10 against the penetration of moisture is furtherimproved by applying the polyethylene jacket 22 to the outwardly facingmajor surface of the adhesive copolymer film 21 under extrudingtemperatures which are designed to yield optimum bonding of thepolyethylene to the laminate 13.

Moreover, the sealed seam 18 along the overlapping edges of the laminate13 produces a tubular member having improved strength characteristicswhich gives prolonged useful life although subjected to repeatedbending.

The construction of the tubular member 10 in accordance with theprinciples of this invention gives a reliably sealed seam 18. During theforming of the temperature laminate 13 to surround the core 12, variouslubricants are used in the equipment. If one of the major surfaces werebare, the lubricants may contaminate the surface of the portion thereofthat bonds with an adjacent contiguous portion of the other majorsurface. This contamination detracts from the development of a reliableadhesive bond between the adhesive on the one major surface to the baredother surface. By using a stripe 19 so as to obtain anadhesive-to-adhesive bond, as opposed to adhesive-tometal, at theoverlap, this problem is overcome. Moreover, at line speeds now in use,it is difficult to obtain a reliably sealed adhesive-to-metal seam.

The construction of the cable 10 in accordance with this invention alsofacilitates the grounding of the tube at 2. splice location. Forexample, during installation and at a splicing location, the jacket 22and laminate 13 may be slit and pulled away from the core 12 as shown inFIG. 3. Then an installer inserts a grounding ring 23 having ears 24under and in electrical engagement with the bared portion of theinwardly facing major surface 16 of the tape 14.

Other types of tube construction which embody the principles of thisinvention, may require that the outwardly facing major surface 17 of thelaminate 13 be barred. Referring now to FIG. 4, construction includesconductors 11 and an inner polyethylene jacket 25 which encloses theconductors. The adhesive copolymer film 21 is coated across the entirewidth of the inwardly facing major surface 16 with the stripe 19 appliedalong one longitudinal edge of the outwardly facing major surface 17. Inthis way, the major surface 16 may be bonded intimately to the materialof the core 12 while the jacket 22 is extruded over and in directcontact with the major surface 17.

METHOD OF MAKING In the method of making a tubular member 10 whichembodies the principles of the present invention, aluminum sheet stockmay have a film 21 of ethylene acrylic acid copolymer precoated acrossone major surface 17 thereof. The adhesive material in the film 21 hasthe ability to develop an adhesive bond at a predetermined temperatureabove ambient temperature. The precoated aluminum is taken up in a roll(not shown) and slit into tapesize widths, each of the tapes 14 havingone major surface 17 precoated with a film 21 of ethylene acrylic acidpolymer.

An aluminum tape 14 precoated across the entire width of one majorsurface 17 thereof, with a first adhesive copolymer material, isavailable commercially such as, for example, from the Dow ChemicalCompany under the designation Zetabond. A stripe 19 of a second adhesiveethylene acrylic acid copolymer is applied from a solution and precoatedalong a longitudinal edge portion of the other major surface 16 thereofwhich is to form the overlapped seam 18 with a portion of the outwardlyfacing major surface. Then successive portions of the tape 14 areadvanced into a tube forming device, designated generally by the numeral26 (see FIG. 5).

Referring now to FIG. 5, the metallic tape 14 is wrapped longitudinallyby the tube forming device 26 to enclose the core and to form theoverlapping seam 18 between the inwardly facing major surface 16 of thestripe and the outwardly facing major surface 17 thereof. As can be seenin FIG. 1, the tape 14 is wrapped about so that the radius of curvatureof the tape is substantially equal to the radius of curvature of thecore. Then the enclosed core 12 is advanced to, and through, aconventional plastic extruder, designated generally by the numeral 27,which is used to extrude the circumferential jacket 22 of polyethyleneover the metallic tape 14 of the laminate 13. This raises thetemperature to the predetermined temperature and causes an adhesive bondto be developed between the adhesive materials on the overlappingportions of the opposite surfaces of the tape.

Molten polyethylene may be fed from the extruder 27 at a temperaturue offrom 357 F. to 475 F. It is more desirable to restrict the temperaturerange to one of 25 F. between 425 F. and 450 'F. There is sufiicientheat within the polyethylene so that the heat transfer takes placethrough the coplymer film 21 contiguous the jacket 22 through themetallic tape 14 and the stripe 19 to melt the portion of the film inthe seam 18 to bond to the stripe. Simultaneously, the film 21contiguous the jacket 22 is caused to develop an adhesive bond with thejacket to achieve a fully bonded sheath.

After the polyethylene jacket 22 has been extruded over the laminate 13,provisions must be made to prevent an excessive amount of heat flowingfrom the hot plastic jacketing material inwardly toward the core. Thissometimes damaging heat flow is accomplished by rapidly chilling theplastic jacket 22, with any of several apparatus (not shown) well knownin the art.

Alternately, the overlapped bonded seam 18 may be formed independentlyof the extrusion of the jacket 22. Successive portions of the metallictape 14, precoated with the stripe 19 and film 21 on the major surfaces16 and 17, respectively, are drawn into an induction-heating unit (notshown) similar to those units disclosed in US. Pats. 2,758,189,2,801,316 and 2,925,485 which issued on Aug. 7, 1956, July 30, 1957 andFeb. 16, 1960, respectively, to D. A. Hughes. Other types of apparatuswhich employ flame heating or hot air may be used to apply heat tosuccessive portions of the seam 18.

As the metal covered core unit 12 is passed through theinduction-heating unit (not shown), high frequency magnetic fieldsdevelop currents within the seam portion of the laminate 13, to heat theseam. By properly controlling the power with conventional control means(not shown), sufficient heating may be provided to accomplish bonding inthe seam portion without degradation of the copolymer. A water-quenchingstation (not shown) may be located immediately adjacent the exit end ofthe induction-heating unit (not shown) to spray water at ambienttemperature onto the seam portion to cool the seam while maintainingpressure therein. Any moisture on the laminate 13 is removed to preparethe now enclosed core 12 for a jacketing operation.

After the metallic tape 14 is formed into a tubular shape with a bondedoverlapped seam 18, the subassembled unit may subsequently have apolyethylene jacket 22 applied to the outwardly facing major surface ofthe copolymer film 21. One of the advantages in using the two stepoperation of heating and later jacketing is that the integrity of thesealed seam 18 can be checked before the polyethylene jacket 22 isapplied. Various techniques can be used to check the integrity of theadhesive seal. One technique is described in US. Pat. 2,988,917 issuedon June 20, 1961 to C. A. Hallam et al.

The use of a forming, sealing and seam integrity checking system,independent of a jacket extrusion operation, allows for starts and stopsto make repairs without impairing the extrusion operation. Ifcircumstances were to make it unimportant to be able to start and stopthe forming and sealing operation, the application of the jacket 22could be accomplished in a tandem operation without intermediate reelingof the core unit 12. A conventional device (not shown) for checking theintegrity of the adhesive seal could be used in a scheme wherein faultyareas were marked so that they could be repaired or cut out of thetubular member after the jacket 22 has been applied.

The tubular member 10 may also be assembled, employing the principles ofthe method of this invention, to provide for grounding the outwardlyfacing (see FIG. 4) major surface 17 of the metallic tape 14.Accordingly, the precoated tape 14, is wrapped about the core 12 tooverlap the stripe 19 along a longitudinal peripheral edge portion ofthe outwardly facing major surface 17 of the tape with the copolymerfilm 21 on the inwardly facing major surface 16. Then the jacket 22 isextruded over the laminate 13 in intimate contact with the exposedoutwardly facing surface 17 of the tape 14.

In one example of a tubular member 10 manufactured in accordance withthe principles of this invention, an aluminum tape 14 having a width offrom 8 /2 to 8% inches and a thickness of from 6 to 8 mils is precoatedwith an ethylene acrylic acid copolymer to form a film 21 which has athickness of approximately 2 mils. Then the precoated tape 14 is coatedwith a solution of adhesive copolymer having a high acrylic acid contentto form a stripe 19 on the major surface 16 of the tape. The stripe 19has a thickness of /3 to /2 mil and has a width of one inch. The barrierlaminate including the tape 14 having the stripe 19 and film 21 thereinwas wrapped longitudinally about an advancing core having a diameter of2.45 inches. Then a polyethylene jacket 22 was extruded over theshielded core to complete the cable 10.

It would be within the scope of this invention to form a tubular memberwithout an outer or inner jacket from a metallic tape by wrappingsuccessive portions of the tape into a tubular shape having anoverlapped seam such that no portions of the tape are retroflexed. Thetape is precoated with an adhesive material on at least part of an edgeporion of one of the major surfaces of the tape facing the overlappedseam, and precoated with an adhesive material on at least part of theother major surface which forms the overlapped seam wth the one majorsurface such that the adhesive materials are caused to develop a bondalong the overlapped seam. The remaining portion of the other majorsurface of the tape is at least partially bare.

The tape from which the tubular member is formed could have an adhesivematerial applied over the entire transverse width of the outwardlyfacing surface. Of course, in that instance, the adhesive material onthe outwardly facing major surface could conceivably act as aninsulating barrier to the transfer of heat to the abutting adhesivematerials along the overlapped seam. In order to transfer the necessaryheat through this potential insulating barrier and achieve a suitablebond along the overlapping seam, it may be necessary to provide anexcessive amount of heat or allow the heat transfer to take place over alonger period of time. This latter course of action can only be achievedby decreasing the linear rate at which the elongated member movesthrough the manufacturing process. A decrease in the feeding or coolingrate causes a decrease in production output or increase in floor spacerequired with accompanying increase in cost of the manufactured product.

Should there be problems in heat transfer to the seam, it would bewithin the scope of the invention to omit the adhesive material on theoutwardly facing major surface, for example, along an edge portionthereof opposite the overlapped seam. Then heat could be applieddirectly to uncoated successive portions of the metallic tape.

It is to be understood that the term tubular member as used in thespecification and claims includes not only a cable having a core, but atape formed into a tubular shape without a core as well as a singleconductor having insulation applied thereover.

It is to be understood that the above-described embodiments are simplyillustrative of the invention and that many other embodiments can bedevised without departing from the scope and spirit of the invention.

.1 1 What is claimed is: 1. A method of manufacturing a tubular member,which comprises the steps of:

advancing successive sections of at least one longitudinal tape along apredetermined path; forming successive portions of the tape into atubular shape with at least one overlapped seam and such that the radiusof curvature of the tape is substantially equal to the radius ofcurvature of the tubular shape, the tape having inwardly and outwardlyfacing major surfaces, the tape having a first adhesive materialprecoated on at least part of an edge portion of one of the majorsurfaces of the tape forming the overlapping seam, the tape also havinga second adhesive material precoated on at least part of the other majorsurface of the tape along an edge portion thereof with the secondadhesive material on the other facing major surface being at leastadhesively bonded to the portion of the other facing major surface ofthe tape which forms the overlapped seam with a portion of the one majorsurface, the remaining portion of the other major surface of the tapebeing at least partially bare, the first and the second adhesivematerials on the major surfaces capable of developing an adhesive bondalong the overlapped seam at a predetermined temperature to seal thescam, the adhesive materials consisting essentially of ethylene acrylicacid copolymers with the second adhesive material having a melt indexand an acrylic acid content which are substantially greater than themelt index and the acrylic acid content, respectively, of the firstadhesive material; and applying heat to successive portions of theoverlapped seam to elevate the temperature to the temperature at whichthe adhesive bond occurs. 2. A method of manufacturing a tubular member,which comprises the steps of:

advancing successive sections of at least one longitudinal tape along apredetermined path; forming successive portions of the tape into atubular shape with at least one overlapped seam and such that the radiusof curvature of the tape is substantially equal to the radius ofcurvature of the tubular shape, the tape having a first adhesivematerial precoated on the outwardly facing major surface of the tapeacross the entire transverse width thereof, the metallic tape alsohaving a second adhesive material precoated on the inwardly facing majorsurface of the metallic tape along an edge portion thereof with theadhesive material on the inwardly facing major surface beingsubstantially restricted in location to and being adhesively bonded tothe portion of the inwardly facing major surface of the tape which formsthe overlapped seam with a portion of the outwardly facing majorsurface, the remaining portion of the inwardly facing major surface ofthe tape being bare, the first and the second adhesive materials on theoutwardly and inwardly facing major surfaces, respectively, beingcapable of developing an adhesive bond along the overlapped seam at apredetermined temperature to seal the scam, the adhesive materialsconsisting essentially of ethylene acrylic acid copolymers with thesecond adhesive material having a melt index and an acrylic acid contentwhich are substantially greater than the melt index and the acrylic acidcontent, respectively, of the first adhesive material; and applying heatto successive portions of the overlapped seam to elevate the temperatureto the temperature at which the adhesive bond occurs. 3. The process ofmanufacturing a tubular member of claim 2,

12 wherein heat is applied to successive portions of the overlapped seamby extruding a jacket of polymeric material over the outside of themetallic tape, and permitting the temperature of the portion of thejacket adjacent to the metallic tape to remain at least at thepredetermined temperature for at least a predetermined period of time,the combination of the predetermined temperature and the predeterminedtime being such that a sufiicient temperature elevation occurs in theadhesive materials at the overlapped seam so that the adhesive materialsdevelop and bond to each other and such that the adhesive material onthe outwardly facing major surface bonds adhesively to the jacket, andwherein the predetermined temperature at which the adhesive bonds occursisless than the temperature at which the jacket is extruded over thetape.

4. The process of manufacturing a tubular member of claim 2, which alsoincludes the step of:

maintaining a proper positional relationship between the adjacent matingportions of the major surfaces of the metallic tape which face eachother at the overlapped seam.

5. The method of claim 2, wherein the thickness of the precoating offirst adhesive material is substantially greater in thickness than theprecoating of second adhesive material.

6. The method of claim 2, wherein the second adhesive material iscapable of being applied in the form of a solution to the metallic tape.

7. The method of claim 6, wherein the copolymer solution is a high meltindex ethylene acrylic acid copolymer of greater than 15 percent byweight acrylic acid in water solution which contains ammonium hydroxide.

8. The method of claim 6, wherein the second adhesive material may beprecoated onto the tape as a salt solution of an acrylic acid.

9. The method of claim 8, wherein the salt is an ammonium salt.

10. The method of claim 8, wherein the salt is an alkali metal salt.

References Cited UNITED STATES PATENTS 3,574,016 4/1971 Wahlberg 156-543,534,149 10/1970 Peacock et a1 174105 R 3,507,978 4/ 1970 Jachimowicz174105 R 3,459,877 8/1969 Bullock et al 156----54 3,332,138 7/1967Garner 15654 3,424,631 1/ 1969 Peacock 1565 6 3,325,589 6/1967 Mildner15654 3,291,891 12/1966 Sharp 174107 3,274,329 9/1966 Timmons 174-1073,264,272 '8/1966 Rees 117--127 3,233,036 2/1966 Jachimowicz 1741073,215,678 11/1965 Adelman 260-80.5 3,032,604 5/1962 Timmons 174107FOREIGN PATENTS 1,034,730 7/1958 Germany.

CHARLES L. VAN HORN, Primary Examiner B. I. LEWRIS, Assistant ExaminerU.S. Cl. X.R.

